Progesterone is a steroidal hormone that regulates many biological processes. Many of the physiological effects of progesterone are mediated by progesterone receptors (PRs). Interaction of progesterone with progesterone receptor can cause activation of the receptor. This can cause the progesterone receptor to be transported from the cytoplasm into the nucleus. In the nucleus, the progesterone receptor can function as a transcriptional activator, which can cause increased expression of specific gene targets.